Approximately 1-5% of all high school and college-aged women in the United States are affected in some way by a pathological dietary practice (Harrison K., Cantor J. J. Commun. 1997, 47:40: Thomsen S. R., McCoy J. K., Williams M. Eat. Disord. 2001, 9:49). The most common pathological dietary practices are anorexia nervosa and bulimia nervosa. Anorexia nervosa is characterized by an intense fear of weight gain and extremely low body weight. This fear is driven by a distorted view of body image and leads to a denial of the pathological condition (American Psychiatric Association. Diagnostic and Statistical Manual for Mental Disorders. APA Press: Washington, D.C., 1994, 2000; Vitousek K. B., Daly J., Heiser C. Int. J. Eat. Disord. 1991, 10:647). Bulimia nervosa is characterized by recurrent cycles of binge eating and purging, through the use of self-induced vomiting, laxatives, enemas, and/or diuretics (American Psychiatric Association. Diagnostic and Statistical Manual for Mental Disorders. APA Press: Washington, D.C., 1994, 2000; Austin S. B. Psychol. Med. 2000, 30:1249; Fairburn S. G., Harrison P. J. Lancet 2003, 361:407). A small percentage, approximately 6-8%, of bulimia nervosa patients are non-purging and use excessive exercise and/or fasting after a binge to offset the caloric intake. While individuals with anorexia nervosa have a low body weight, individuals with bulimia nervosa can be of any body type making clinical detection more difficult.
The detection and treatment of anorexia nervosa and bulimia nervosa have been hampered by the lack of reliable clinical tests for these disease states. Currently, the diagnosis of anorexia nervosa and bulimia nervosa is based upon self-reporting, questionnaires, and some severe health indicators. The psychological questions are more highly weighted, because the physiological indicators are more subjective. This is especially true of pre and early adolescent individuals, where physiological indicators, body mass index values and menstrual cycles, are not routine. Standard questionnaires and interviews designed to assess anorexia nervosa and bulimia nervosa rely on accurate self-reporting by the patient. Common to both anorexia nervosa and bulimia nervosa, is an element of denial. Since diagnosis is based upon self-reporting and questionnaires, an affected individual usually does not come to the attention of a medical practitioner until a serious associated medical condition or psychological problem appears. Early detection of anorexia nervosa and bulimia nervosa would help doctors identify eating disorder sufferers before the associated nutritional deficiencies can cause severe health problems.
When X-rays come in contact with matter, the resulting scattering and change of intensity of the rays can yield significant structural information about the composition of the sample. In fiber X-ray diffraction, the diffraction pattern consists of a series of intensity rings perpendicular to the fiber axis. Biological fibers contain elongated molecules along the axis of the fiber that are aligned parallel to each other. Small Angle X-ray Scattering (SAXS) diffraction has been used to examine the filament structure of human hairs as far back as 1995 (Wilk K. E., James Amemiya Y. Biochimica et Biophysica Acta 1995, 1245:392) Hair samples from individuals who have been exposed to mercury exhibit altered SAXS diffraction patterns. While mercury does not interfere with the intermediate filaments of hair, it does disrupt the proteoglycan layer in the extra cellular matrix of hair, affecting SAXS patterns (Xing X., Du R., Li Y., Li B., Cai Q., Mo G., Gong Y., Chen Z., Wu Z. Environ Sci Technol 2013, 47:11214). Although significant changes to the hair structure can be detected by X-ray diffraction, a recent study reported that the X-ray diffraction patterns of hair from healthy individuals are highly consistent (Yang F. C., Zhang Y., Rheinstadter M. C. Peer J 2014, 2:e619).
Hair follicle cells have a high metabolic activity. As a result, hair growth and development can be affected by dietary or micronutrient deficiencies. Previous work has shown that deficiencies in vitamin A, vitamin B12, biotin, vitamin C, zinc, selenium, and essential fatty acids can alter the hair's growth rate, pigmentation, and structure (Goldberg L. J., Lenzy Y. Clinics in Dermatology 2010, 28:412; Ginner A. M. Dermatol Clin 2013, 31:167). In diagnosing these deficiencies, typically the hair is examined for such characteristics as hair diameter, hair pigmentation, decreased hair quality, increased fragility, brittleness, or the ease with which it can be pulled from the scalp, However, these diagnostic signals are highly subjective because of a lack of laboratory standards or clear correlations between nutritional status and the previously stated characteristics (Ginner A. M. Dermatol Clin 2013, 31:167).